Cardiovascular system - Blood Anatomy - Chapter20

The Cardiovascular system is comprised of the heart, blood vessels, & blood The heart acts as a “pump”, creating pressure which causes blood to move through the blood vessels of the body, allowing O2 & nutrients to be distributed to, & wastes removed from, body tissues

Physical characteristics of blood Fluid connective tissue matrix – “plasma” with dissolved proteins cells & cell fragments – “formed elements” temperature – 38o C 5x more viscous than H2O pH – 7.35-7.45

Functions of Blood Regulation Protection Transportation O2/CO2 nutrients/wastes enzymes hormones Regulation body temperature pH & ion composition of interstitial fluid intracellular fluid volume Protection defense against pathogens restriction of fluid loss at injury sites

Composition of Blood 55% Plasma – liquid component of blood 45% Formed elements – cells/cellular fragments Erythrocytes – red blood cells (RBCs) Leukocytes – white blood cells (WBCs) Platelets – (thrombocytes)

Plasma

Formed Elements granular (B & T) agranular

(pluripotent stem cell) Hemopoiesis Megakaryoblast

Erythrocytes (RBCs) around 5 million RBCs per mm3 blood Biconcave shape, flexible cells around 5 million RBCs per mm3 blood average “life span” of 120 days Cells contains cytosol, no nucleus/organelles; filled with Hemoglobin (Hb)

Hemoglobin Hemoglobin allows for transport of O2 & CO2

As RBCs get damaged/worn out, they must be removed from circulation & replaced About 1% of the circulating RBCs are replaced each day, at at rate of about 3 million RBCs per second Worn out RBCs are removed by phagocytic cells in the liver, spleen & bone marrow Most of the RBC’s hemoglobin is recycled, the pigmented part (heme) gets converted to bile pigments

Erythropoiesis New RBCs are made in red bone marrow (myeloid tissue) by process of erythropoiesis stimulus for erythropoiesis is hypoxia detected by cells of kidney

Leukocytes (WBCs) More like “typical” cells with single nucleus, organelles 5 types of WBCs characterized as granular or agranular all function in defense average 6000-9000 WBCs/mm3 of blood variable “life” span depending on type of WBC- days (neutrophils) to decades (lymphocytes); in sick person, some WBCs live minutes to hours

Differential Count & Functions of WBCs “WBC differential count” – normal range (in percentage) of WBCs in the peripheral circulation differential count will vary during specific types of disorders, depending on which type of WBC responds WBC response based on functions of specific type

Differential Count & Functions of WBCs Neutrophils - 50-70% Lymphocytes – 20-30% Monocytes – 4-8% Eosinophils – 2-4% Basophils - <1% function in acute bacterial infections; phagocytic function in chronic bacterial infections; migrate into tissues to become “wandering macrophages” active against parasites & elevated in allergic reactions; destroy antibody-coated antigens by phagocytosis release chemicals (histamine, heparin) during tissue inflammation

Differential Count & Functions of WBCs Lymphocytes – 20-30% Function in “immunity” – specific resistance to disease T cells- involved in “cell-mediated (aka cellular) immunity”; defense against abnormal cells & intracellular pathogens B cells- involved in “antibody-mediated (aka humoral) immunity”; defense against pathogens (Ag’s) in body fluids (blood/lymph)

Platelets (Thrombocytes) Cellular fragments (cell membrane “packet” filled with cytoplasm) from large Megakaryocytes found within bone marrow around 350,000 platelets/mm3 platelets circulate for 9-12 days before being removed from circulation platelets function in hemostasis– the processes that stop bleeding from damaged blood vessels – including “platelet plug formation” and “coagulation”